Many agricultural combines use a rotary threshing or separating system. The system typically includes at least one rotor drivingly rotated within a perforated concave spaced radially outwardly thereof. The rotor will often have a frusto-conical inlet end having a helical flight or flights therearound for conveying a flow of crop material into a space between the rotor and the concave. The main body of the rotor will typically have one or more cylindrical or other shaped outer surface portions including threshing elements, which can include, for instance, rasp bars, which protrude radially outwardly therefrom into the space and which are arranged in a pattern or array for conveying a mat of the crop material along a helical path through the space, while cooperating with features of the concave, e.g. protrusions such as bars or ribs, to separate larger components of the crop, namely crop residue commonly referred to as straw, which includes stalks, stems, cobs and the like, from the smaller grain and material other than grain (MOG). The threshing elements are typically supported on brackets or mounts that are welded or otherwise mounted to the outer surface of the main body segment.
An important parameter for a successful threshing performance is the gap between the radial outer portions of the threshing elements, and the radial innermost features or portions of the surrounding concave. The setting of this gap is an operator function, and will typically be finely adjusted within a range of just a fraction of an inch or a few millimeters before or during operation to achieve a desired threshing capability or performance. Generally, if the gap is set too large, not enough grain will be separated from the straw, resulting in more grain loss. If the gap is too small, threshing quality may suffer, and in particular, the grain may be subjected to damage, particularly cracking, which is highly undesired in most instances. If there are irregularities in the outer surface of the rotor on which a threshing element is mounted such that the threshing element is radially inwardly or outwardly of its desired position, as the rotor is rotated past a particular region of the concave, the gap will vary.
It is well-known to make the main body segment of a rotor from a sheet or sheets of metal, by forming the sheet or sheets into a tube. In the known constructions, the juncture of the edges of the sheet or sheets follows a straight line, or a helical line around the tube, and is typically a welded seam. Also typically in the known constructions, the desired layout of the threshing elements about the outer surface of the main body segment, and the number of threshing elements desired, necessitates welding at least several of the mounting elements for the threshing elements in overlaying relation to the welded seam. As result, to attempt to ensure that the threshing element mounts will position the threshing elements mounted thereto at the proper radial position or distance from the surface, any portions of the welded seam onto which threshing element mounts are to be attached, will typically be ground flush with the outer surface. A disadvantage is that this adds a manufacturing step, and often, an inspection step, one or both of which may have to be repeated to achieve the desired surface level. Another possible disadvantage is that the weld seam may be weakened, so as to be less resistance to damage from rocks inducted by the threshing system.
Accordingly, what is sought is a manufacturing method for a rotor, and a resulting rotor construction, which overcomes one or more of the disadvantages set forth above.